Invasive Species Management

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Need Noxious Weed Advice?

We are able to answer calls and questions. Our hours are Mon -Thur 6:30 am - 5 pm.  See our contact information on the right-hand side of this page.

What We Do

Orange hawkweed flowerhead.The Jefferson County Invasive Species Management program provides the public with information and offers solutions for managing invasive species and supports good stewardship of the land.  

We ensure the compliance with Colorado’s noxious weed, forest pest, and agricultural vertebrate pest regulations on private, county, and state lands.  We also provide technical assistance and support to county departments who are responsible for managing county owned lands.

The program coordinates with private, local, state, and federal agencies to achieve regional pest control.

Who We Are

Canada thistle flower.Our staff includes the Invasive Species Management Coordinator and limited summer help.

Weed of the Month

Each month we will feature a noxious weed to help landowners identify weeds they may encounter on their property.

Cypress spurge

February 2023

Cypress Spurge

Euphorbia cyparissias

Cypress spurge is a List A perennial that is an escaped ornamental.  Originally from Eurasia, it was first reported in the US in 1858 and in Colorado in 1895.  It is not very common in Colorado but can be found in landscaped areas and has been found escaping into natural areas.

The plants usually grow to less than 16 inches tall but may reach up to 26 inches tall.  It forms dense patches of multiple slender stemmed plants. The stems may branch in the upper half of the plant. Leaves are narrow, less than 1/8 inch wide and about 1 inch long.  Flowers are reduced and have a pair of yellowish-green bracts beneath.   Flowers occur in spring through early fall and become reddish later in the season.  Roots can be 15 feet deep and woody rhizomes spread horizontally up to 35 feet.  

There are both seed and non-seed producing populations.  The seeded varieties form seed pods that contain one to three seeds. The sticky seeds explode when the pods ripen.  The seed producing varieties will sometimes hybridize with Leafy spurge (Euphorbia virgata formerly known as Euphorbia esula).  The genetics of Cypress spurge are complicated including both diploid and tetraploid types.

The plants contain toxic latex that is irritating to skin and eyes and causes rashes and blisters on lips and skin.  Most native animals and livestock do not feed on it.



USDA Fire Effects

Wisconsin Dept of Natural Resources

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A Landowner's Guide - Developing a Noxious Weed Management Plan

We developed this guide to assist landowners.  The information provides steps to develop a management plan for properties that have noxious weeds.

Download your copy

yellow_flag_iris Weed Spotter

The Weed Spotter program is a citizen science based effort to detect 6 high priority species on Jeffco Open Space parks.  Learn more at our Citizen Science page.